Mechanofluorochromic behaviours of functionalized carbazole‐based difluoroboron compounds with different aryl substituents moieties

Abstract

To better understand the relationship between molecular structure and mechanofluorochromic characteristics, three carbazole‐based N^O‐chelated difluoroboron compounds (Cz‐S‐BF2, Cz‐PhNp‐S‐BF2, and Cz‐BNp‐S‐BF2) with different aryl substituents moieties were designed and synthesized. The mechanofluorochromic behaviours of Cz‐S‐BF2 (luminescence from bluish‐green to yellowish‐green, emission from 504 to 535 nm) without aryl substitution and Cz‐PhNp‐S‐BF2 (luminescence from green and yellow, emission from 521 to 557 nm) with a phenyl‐naphthalene group underwent reversible conversion using the grinding–fuming process. For Cz‐BNp‐S‐BF2 this was not apparent due to the well coplanarity of the binaphthalene moiety. Mechanofluorochromic properties were demonstrated through XRD patterns measurement. We envisage that this study will provide a practicable reference to acquire organic molecules with mechanofluorochromic characteristics.

Mechanofluorochromic behaviors and data security protection properties of salicylaldimine‐based difluoroboron complexes with different aryl substituents

“…Nevertheless, either the luminescence color or the emission wavelength of ts‐2NA BF 2 had little change under external mechanical stimulation. This was consistent with our previous reports that a better coplanarity originated from the binaphthyl substituent group [36]. Meanwhile, we found that the emitting colors and emission peaks of ts‐Ph BF 2 and ts‐TPA BF 2 could be recovered to their original states by CH 2 Cl 2 vapor fuming for 30 s, which indicates that ts‐Ph BF 2 and ts‐TPA BF 2 had reversibly MFC behaviors.…”

“…Because ts‐TPA BF 2 displayed the most distinct redshift (21 nm) under external mechanical stimulation and remarkable reversible chromatism by grinding–fuming process compared with the other three complexes, ts‐TPA BF 2 ‐based ink‐free rewritable paper for information encryption and decryption was explored. According to previous reports [36, 49], a Whatman filter was immersed into 10 mL of CH 2 Cl 2 in which 10 mg of ts‐TPA BF 2 solid powder was dissolved for 10 min, and then the immersed filter paper was dried by airing on an A4 paper as safety paper. The prepared safety paper emitted yellow luminescence under 365 nm irradiation, as shown in Figure 8.…”

“…Furthermore, if the MFC materials exhibited significant color changes under external mechanical stimuli, the high‐contrast MFC materials could be explored in the application of rewritable data storage [28–35]. In previous work, we found that the different aromatic groups (phenyl‐naphthyl and binaphthyl) in the fourth position of the carbazole skeleton had a remarkable influence on the fluorescence spectra shifts under mechanical stimulation; however, they were not applied in data security protection in ink‐free rewritable paper due to the prepared security paper without color switching or emitting color disagreement with solid powders [36]. Therefore, further exploration was needed to determine whether materials with MFC behaviors can be applied in rewritable data storage.…”

Reversible Red‐/Blue‐Shifted Mechanofluorochromic Properties of Indole‐Based Difluoroboron Compounds with Aggregation‐Induced Emission

“…In previous studies, we found that the introduced different aryl substituents moieties in 3‐position of carbazole skeleton had a significantly influence on the MFC behaviors of the carbazole‐based salicylaldimine difluoroboron compounds due to different steric hindrance effects, [22] and the indole‐based difluoroboron compounds with triphenylamine group not only exhibited remarkable MFC behavior, but also could be achieved rewritable storage [23] . Therefore, we envisaged that indole unit was modified using aromatic groups to achieve excellent MFC performance.…”